Papers by Author: H. Wang

Abstract: 1 mol% Er3+- and 0–10 mol% Y3+-codoped Al2O3 powders is prepared in a non-aqueous sol–gel method. Two crystalline types of doped Al2O3,  and θ, are obtained for the 0–10 mol% Y3+-codoped Al2O3 powders sintered at the sintering temperature of 1000 °C by x-ray diffraction analysis. The green and red up-conversion emissions centered at about 550 and 670 nm increase with Y3+ codoping concentration, and the maximal intensity of both the green and red up-conversion emissions is obtained as about 100 and 10 times higher than that of the 1 mol% Er3+-doped Al2O3 powders, respectively. The enhancement in the green and red up-conversion emissions is ascribed to the improved dispersion of Er3+ in Er3+–Y3+-codoped Al2O3 powders.

Abstract: In order to improve the lifespan and performance of the forming mould with low melting point, arc spray forming of stainless steel mould has been advanced. The technical process of spray mould has been investigated, and the correlations among the spray parameters, in-flight characteristics of molten particle and the forming quality have been analyzed in detail. Meantime, the influence of the preheating temperature of the spray mould and the spray angle on the morphology of the splashing particles has been also investigated. The research results indicate that the atomization pressure greatly influences the velocity and granularity of the in-flight particles. The working current greatly influences the particle temperature, and the spray distance influences the temperature and velocity to some extent. A compact spray layer, with a low porosity, little oxide content, and high microhardness, can be obtained by increasing the atomization pressure. The research has a great significance to optimize and control the forming quality of rapid tooling by arc spraying.

Abstract: This paper deals with a new finishing technique called pulse electrochemical finishing technology (PECF) and its application to column surface of carbon steel. PECF makes use of pulse current and neutral electrolyte. There is nearly no wear of the cathode, and nearly no cutting force or cutting heat, which may result in the deformation of wokpiece. The principle of the technique is put forward, and the equipment as well as a typical finished sample is shown in this paper. The key technological parameters of PECF are studied and the favorable values are presented. With the moving cathode PECF technology, the roughness value of ground surface could be reduced from Ra 0.217～1.13μm to Ra 0.041μm. Combined with NC technology, PECF could be applied to the finishing field widely.

Abstract: The dimensional accuracy of electro-discharge machining (EDM) is greatly influenced by the overcut resulting from discharge gap and electrode wear. In order to achieve fine accuracy, it is necessary to estimate the overcut according to an empirical formula. In this paper, experiments in electro-discharge machining were carried out. The effects of parameters on the overcut, such as peak current, pulse duration, were analyzed. Then an empirical formula for the overcut in EDM was established based on the experimental results using the least square method. Finally, reasonable agreement between calculated results and the further experimental results was obtained.